JP3272766B2 - Manufacturing method of Gunn diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing a Gandaio de which is use as an oscillation source of a vehicle-mounted millimeter-wave band.

[0002]

2. Description of the Related Art Gunn diodes used as an oscillation source of a millimeter-wave band radar mounted on a vehicle are substantially parallel to each other.
An operation layer is formed in a semiconductor layer between the individual electrodes, and a structure (or a sandwich structure) of a vertical semiconductor element which operates by applying a current to the operation layer is exhibited. Specifically, FIG.
As shown in the cross-sectional view, an n ⁺ GaAs layer 21, an nGaAs active layer 22 sequentially formed thereon by epitaxial growth, an n ⁺ GaAs contact layer, and electrodes formed on upper and lower n ⁺ GaAs surfaces An element having a structure composed of 24 and 25 is thermocompression-bonded with a metallized layer or the like interposed on a heat sink 23 having good thermal conductivity in an overturned (upside-down) state so that the operation layer 22 side faces down. A current is caused to flow between the beam lead 27 and the metallized layer.

As a method for mass-producing the Gunn diode having the structure shown in FIG. 3, first, the above-mentioned vertical structure is formed on a GaAs substrate, and then this substrate is subdivided into a desired size to obtain a desired number of small areas. A method of obtaining a Gunn diode is employed. Various methods of this subdivision are known, but they are roughly divided into the following three types.

A. A semiconductor substrate on which a vertical structure of a gun diode is formed is fixed on a holder, and a groove having a depth less than the element thickness is formed using a diamond cutter or the like, and then cracking is performed to form a plurality of small pieces of a gun diode. (Japanese Patent Application Laid-Open No. 51-28284, etc.) The substrate on which the vertical configuration of the Gunn diode is formed is fixed on a rigid holder such as a dummy wafer, and a groove having a depth reaching the holder is formed using a diamond cutter or the like. A method of separating into small pieces of gun diodes (Japanese Patent Laid-Open No. 57-15439, etc.) C. A substrate having a vertical structure of gun diodes having discrete electrodes formed on both surfaces is fixed on a holding body. Then, one main surface side is mesa-etched using the discrete electrodes formed on this main surface as a mask, and then the other main surface side is mesa-etched using the discrete electrodes formed on this main surface as a mask. (See Japanese Patent Application Laid-Open No. 57-21870).

[0005]

The above-mentioned conventional methods A and B
In addition, a step of removing the surface layer on the side surface where cracks and lattice defects have occurred due to mechanical cutting and cracking is required. This is because, in a vertical semiconductor device that operates at a high frequency such as a Gunn diode, most of the current flows around the device due to the skin effect, so that the quality of the surface layer on the side surface greatly affects the characteristics. However, in both of the conventional methods A and B, since the elements have already been separated by cracking or full cut, this etching step has to be performed for each of a large number of separated elements, which requires only labor and time. However, there is a disadvantage that processing conditions such as etching time tend to vary from element to element.

In the method C described above, the mesa etch is performed from both the front and back sides of the substrate on which the vertical structure is formed. Therefore, as shown in FIG. At the same time, a pointed portion is formed at the middle portion in the thickness direction, and there is a disadvantage that the electric field is concentrated there and the characteristics are likely to be deteriorated. In FIG. 4, 31 is an original semiconductor substrate, 32 is an operation layer, 33 is a contact layer, and 34 and 35 are electrodes.

Further, the method C has a drawback in that the number of manufacturing steps increases because it is necessary to repeat the mesa etching twice on the front side and the back side while reversing the front and back of the substrate. Further, in this method, since the electrode is used as a mask at the time of etching, it is necessary to form a patterned electrode on both sides in advance, and this also has a disadvantage that the number of manufacturing steps is increased.

[0008]

According to a method of manufacturing a Gunn diode according to the present invention, a surface of a semiconductor substrate on which a Gunn diode is formed is coated with a resist layer, and the back surface is bonded via an adhesive layer. It is adhesively fixed on a rigid holder, and is fully cut up to an adhesive layer together with the resist layer, thereby separating into a gun diode element group while maintaining the adhesively fixed state on the holder. by etching the respective side faces formed by mechanical cutting by immersing the Gunn diode element groups remain etchant maintaining the bonded state onto the holding member has, cancer after the completion of the etching
A desired size and a desired number of Gunn diodes are obtained by removing the diode element group from the holder.

[0009]

According to the present invention, firstly, moth semiconductor substrate Gandaio de is formed via an adhesive layer, such as a wax
It is fixed on a rigid support such as a lath plate and the surface is covered with a resist layer. Next, this substrate is fully cut from the resist layer on the front side to the adhesive layer on the back side, and a small area gas is maintained while maintaining the adhesive fixed state on the holder.
Separated into diode element groups. Subsequently, each side formed by mechanical cutting is etched by immersing the entire separated gun diode element group in an etchant while maintaining the adhesively fixed state on the holder, and at the time of cutting, The side surface layer including the generated cracks and lattice defects is removed. After the etching is completed, the Gunn diode element <br/> transducer group by a method such as to melt the adhesive layer is removed from the holding member, Gandaio desired number
De can be obtained.

[0010]

FIG. 1 is a sectional view for explaining a method for manufacturing a gun diode according to an embodiment of the present invention.

First, an operation layer is formed substantially in parallel with a front surface of a GaAs substrate having a substantially uniform thickness, and one and the other of a pair of electrodes are formed on the front and back surfaces of the substrate, respectively. Thereby, a vertical structure of a Gunn diode is formed on the surface and inside of the substrate. That is, FIG.
As shown in FIG. 3, an nGaAs active layer 12 and an n ⁺ GaAs contact layer 13 are sequentially formed on the n ⁺ GaAs layer 11 by epitaxial growth, and electrodes 14 and 15 are formed on the upper and lower n ⁺ GaAs layers, respectively. .

Next, as shown in FIG. 1B, the substrate on which the vertical structure is formed is bonded and fixed on a glass support 17 by a wax layer 16, and a resist layer 18 for etching is formed on the upper surface side. I do. As the wax layer 16, an appropriate one can be used. For example, a layer commercially available from Nikka Seiko under the trade name of “CB wax” is preferable.

Subsequently, as shown in FIG. 1 (C), the substrate adhered and fixed on the glass holder 17 is rotated together with the resist layer 18 on the surface thereof to the adhesive layer 16 using a rotary diamond cutter 19. It is cut mechanically at predetermined intervals. This mechanical cutting is also performed at predetermined intervals in a direction perpendicular to the paper surface. Thereby, the holder 17
It is separated into a group of Gunn diodes having a rectangular cross-sectional shape while maintaining the state of being adhered and fixed thereon.

Next, as shown in FIG. 1 (D), the separated gun diode groups are fixed on the holder 17 and immersed in an etchant (EC) to etch the respective side surfaces, thereby mechanically separating the groups. The damage layer on the side surface caused by the cutting is removed. As the etching solution used at this time, a solution which hardly causes anisotropy due to the crystal plane, for example, a mixed system of phosphoric acid, hydrogen peroxide and water is used.

After completion of the etching, the wax layer 16
When the Gunn diode group is removed from the holder 17 by a method such as melting and removing, the cross-sectional shape orthogonal to the current flow path as shown in the cross-sectional view (A) and the plan view (B) in FIG. A gun diode of a desired size having a shape is obtained.
Further, unlike the case of the mesa etching, since the surface to be etched is only the side surface, the etching proceeds substantially parallel to the original cut surface, and a substantially vertical side surface is obtained.

As described above, the configuration in which the operation layer in the substrate is placed on the upper side, cut and etched by bonding and fixing on the holder is exemplified. However, conversely, a configuration may be adopted in which the operation layer in the substrate is placed on the lower side, and the adhesive is fixed on the holder, cut, and etched.

Although the mechanical cutting is performed by using a diamond cutter, the cutting may be performed by using other appropriate tools such as an ultrasonic cutter.

[0018]

As described in detail above, the present invention
The method of manufacturing a gun diode is mechanically full cut.
The bonded Gun diode element group is fixed on the holder
By mechanical cutting by etching while maintaining the
Configuration to remove the side damage layer caused by
Etching of each of the separated element groups
The labor and time can be greatly reduced compared with the conventional method.
Both have the effect of mass-producing element groups with the same dimensions.
Is played .

A conventional method for performing a mesa etch from both sides
Unlike the above, almost vertical sides can be formed and uniform in the thickness direction
This has the effect that a high current distribution can be realized .

[0020]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining each step of a method for manufacturing a gun diode according to one embodiment of the present invention.

FIGS. 2A and 2B are a cross-sectional view and a plan view showing a structure of a Gunn diode manufactured by the process of FIG.

FIG. 3 is a cross-sectional view for explaining the structure of a Gunn diode which is a typical example of a vertical semiconductor device to which the manufacturing method of the above embodiment is applied.

FIG. 4 is a cross-sectional view illustrating the shape of an element manufactured by one of the conventional methods.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 n ⁺ GaAs layer 12 nGaAs operation layer 13 n ⁺ GaAs contact layer 14, 15 electrode 16 Wax layer for bonding and fixing 17 Holder such as glass 18 Resist layer for etchant (EC)

Claims (2)

(57) [Claims] 1. A gun semiconductor substrate having a substantially uniform thickness
A diode is formed, and the surface of the semiconductor substrate on which the Gunn diode is formed is
Rigid body covered with a dist layer and the back side with an adhesive layer
Adhesive fixing on the holding member, onto the holder by cutting a semiconductor substrate which is bonded and fixed onto the holding body said mechanically in the thickness direction of the semiconductor substrate to said adhesive layer together with the resist layer formed by bonding fixed state separated into Gunn diode element group while maintaining the mechanical cutting by immersing the separated Gunn diode element group in the etchant while maintaining the bonded state to the holding body on Each of the side surfaces is etched, and after the etching is completed, the gun diode element group is detached from the holder to thereby obtain a desired number of gun die.
A method for manufacturing a gun diode , comprising obtaining an arm . 2. The holding body is a glass plate, and the adhesive layer is
2. The ganda according to claim 1, wherein the ganda is a metal layer.
Method of manufacturing iod .